High temperature pressurized coaxial radio frequency connector



July 26, 1960 c. H. CHILD ET AL 2,946,971

HIGH TEMPERATURE FRESSURIZED COAXIAL RADIO FREQUENCY CONNECTOR Filed Dec. 2l, 1956 2 Sheets-Sheet l CLAUDE H. CHILD STANLEY A, PRYGA BY ATTORNEY July 26, 1960 c. H. CHILD ET AL 2,946,971

HIGH TEMPERATURE PREssuRIzED coAxIAL RADIO FREQUENCY CONNECTOR Filed Dec. 2l, 1956 2 Sheets-Sheet 2 ATTORNEY HIGH TEMPERATURE PRESSURIZED COAXIAL RADIO FREQUENCY CONNECTOR claude H. Child and stanley A. rryg, Paramount, Calif., assignors to North American Aviation, Inc.

Filed Dec. 21, 1956, ser. No. 629,863 9 claims. (ci. ess-497) This invention relates to coaxial connectors and' more particularly to a coaxial connector for use with rigid or semi-rigid gas dielectric coaxial lines.

' In most applications, where coaxial connectors are utilized at relatively normal temperatures, the matching problem between the gas dielectric line and the connector is not very ditiicult because a material which has a rela.- tively low dielectric constant can be used to supportv the center conductor in the connector. In applications, however, such as where the connector is to vbe usedr in a missile, where temperatures as high as 600 F. may be encountered, it is necessary that a material which will stand these temperatures be used forfthe center conductor support. It has been found that certain high tem'- perature ceramics will best satisfy such requirements. Such ceramics, however, all have high dielectric constants (in excess of 6). In order to achieve coupling of a radio frequency signal from a gas dielectric line -toa connector with a center conductor support of relatively high dielectric constant without intolerable reliections, it is necessary that some special matching means be utilized. The device of this invention oiers a solution to this problem. This 'is accomplished by specially shaping the support beads and associated portions of the connector so that the transition angles at dielectric boundary surfaces effect reflectionless transmission.

With the device of this invention it is possible to transfer ultra high frequency radio energy with avoltage standing wave ratio of less than 1.2 and a loss of less than .5 db when operating intoa matched load. This can be accomplished while utilizing separator beads fabricated of high temperature ceramics which have dielectric constants in excess of 6. In addition to its excellent matching and high temperature characteristics, the device of this invention is such that it remains airtight when utilized with pressurized lines. It is therefore an object of this invention to provide an improved coaxial connector for use with rigid or semi-rigid gas-filled lines.

It is another object of this invention to provide a coaxial connector Which will function satisfactorily at very high temperatures.

l It is a further object of this invention to provide a coaxial connector which willcouple radio frequency signals with little or no reflections.

It is a still further object of this invention to provide a coaxial connector for use withA gas-filled lines which is airtight and can be utilized-successfully with pressurized lines.

' It is -a still further object of this invention to provide a radio frequency coaxialconnector for use at high temperatures which has low loss and good transmission characteristicsl over a broad frequency range.

It is still another object of thisinvention to provide an easily detachable connector that will operate at high temperatures with little or no reflections'.

Other objects of this invention will become apparent from the following description' taken in connection with the accompanying drawings in which States Patent() Fig. 1 is an illustration of a male version of the device of this invention;

Fig. 2 illustrates a cross section of a male version of the ydevice of this invention represented as cut by a plane 2-2 indicated in Fig. 1;

Fig. 3 illustrates a female version of the device of this invention; v

Fig. 4 illustrates a cross section of a female version of Fig. 6 illustrates wave travel in the device of this inf vention.

Referring to Figs. l and 2, a male version of the con nector as utilized with a gas dielectric coaxial line is shown. The connector consists of an electrically conductive shell 1 with an inner center electrical conductor 4 to form a coaxial line. The center conductor is supported by Y two conical beads 3a and 3b which are fabricated of a and outer shell.

high temperature ceramic. A mica bonded glass such as Mycalex which will stand temperatures in excess of 600 F. is satisfactory. There is a gas dielectric in the spaces 6a, 6b and 6c between the center conductor, ceramic beads This gas can be air or any other suitable gas and can be either pressurized or not depending on insulation breakdown requirements. l

The ceramic beads are bonded to the outer concentric shell at points 8a and 8b and to the center conductor 4 at points 7a and 7b. A high temperature porcelain cement or enamel such as Sauereisen 19 fabricated by the Sauereisen Company, Pittsburgh, Pennsylvania is recommended. To assure a good and durable bond under high temperature operating conditions, it is necessary that such a bonding agent be cured by heating under vacuum.

Referring to Fig. 5, in which a boundary surface 16 between the support beads and a gas dielectric is illus.- trated, the angle 18 at which the incident wave (that coming from .the left hand side in the diagram) enters the dielectric boundary surface is referred to as 01. To assure that signals will pass through the dielectric transition with little or no reection, the conical beads must be so shaped that 01 satisfies the equation,

0 =arc tan little Aor no reflection. This phenomenon is known in theVV art as the Brewster Angle effect and is discussed in the RCA Review, volume l5, pp. 238-25l in an article entitled, Applieation of Brewsters Angle to the Design of Coaxial Line Components for Microwaves byB. A. Dahlman.

Referring to Fig. 6, the path of an electrical wave through the connector is illustrated. The direction of wave travel is perpendicular to themutually perpendicular electric (E) and magnetic (H) elds. As can be seen, the wave enters from the gas dielectric at the left with an angle of incidence 18a. It is refracted with an anglel of refraction 19a as it enters the iirst ceramic separator bead 3a. An equal and opposite refractionoccurs as it leaves the ceramic medium withr an angle of incidence 18b and an angle of refraction 19b. This-processis repeated as the wave enters and leaves the second separator Patented July 26 1960I 3 beads 3b with incident angles 18e and 18d refraction angles 19e and 19d.

Equation (1) will be satisfied if the conical beads are shaped so that the tangents of their base `angles. 20a and 20h are equal to y V ,K1

vangle '22, this 'base' angle must be equal to the angle ofv incidence, 18e. The base angle 20a of the rst beadv 3g;v is

equal to angle A20?; and will give an 1angle of incidence.

18aV which has a tangent yequal to that of angle Y20h.

Still referring to Fig. 6, it is also necessary that the im-V pedance ofthe conical transmission lines formed between the outer conductor r1 at surfaces 8a and 8b and the inner conductor f4 at surfaces v7a and 7b respectively, with the conical separator beads Vas the dielectric in between, be matched to the characteristic impedance of the coaxialV line "being coupled. Such an Aimpedance match can be accomplished by proper choice of the face angles qta (14a and lilb)Y atV the junction of the'conical beadsA with the center conductor, and the lface angles, pb (13a and 13b) at the junction of the connector'beadswiththe 'retaining surfaces in the lconcentric shell. These faces langles are referenced vfrom the longitudinal axis of the center con? ductor as indicated in Fig. 6, and are determined bythev relationship,

where Zc is the characteristic impedance of the conical and coaxial lines to bematched, and K2 is the dielectric constant of the material of the conical separator beads. kWhile Vin practice the characteristic impedance of the conical vline can he made to approach the characteristic impedance `of the coaxial line to be coupled, it is in 'some instances difficult to Vvachieve a yperfect match. -In the device illustrated in Fig. 2, the face angle pb (13a andV 13b, Fig. 6) were made equal to 90 instead of the theoretical 105 to facilitate fabrication. To compensate Vfor shunt capacitance due to slighttmismatch caused by 'such practical design, an undercut v5 is maderin the shell. An effective inductance determined by the length and depth of this undercut 'is thus provided to compensate kfor such shunt capacitance. The Adimensions of this undercut 'can best bek determined experimentally for Yany specific connectorby the cut and try,method.

Referring to Fig. 2, coupling nut 9 ,is usedto secure the connector to itsifemale counterpart. Pin 1S makes connection with a mating receptacle 22 (Fig. 4) on the female connector. Gasket 10 provides a. seat for the outer lshell of the female connector. A cylindrical metal ferrule 11 is used `to form an `airtight connectionbetween coaxial line Zand the connector. The ferrule is tapered on both ends so that it will seat itself against the retainer ring 23 on one end and the sleeve nut 12 on the other. This `ferrule is Ybonded to the very end of the outer conductor ofthe coaxial vline by brazing or'siniilar means. It is then fastened to the'connector'by means of approximately 125 inch lbs. rof torque is applied to this nut 'in tightening it. Y Thejcenter conductor Af-l has `a hol-A low receptacle on its end to receive the vcenter conductor Zlfo'f the coaxial line. Y V

A female version of this connector is illustrated in Figs. 3 and 4. Construction is similar to that of the male type shown in Figs. l and 2 in all respects except that provision is made to mate it with its male counterpart, as is obvious in the illustrations.

Practical embodiments of the devices illustrated in Figs. l, 2, 3, and 4 have been successfully tested. These have conical beads of supramica #555, a mica bonded Y glass with a dielectric constant of 9.3, fabricated by the Mycalex Corp., Clifton, New Jersey. The base angles of these beads (Fig. 6, 20a and 20b) are equal to 7151'. The face angles, oa, (Fig. 6, 14a and 14b) are equal to 147. The face angles, b (Fig. 6, 13a and 13b) are equal to 90. -Y Y The device of this invention can be used at frequencies through the ultra high frequency range'with low losses and insigniiicant standing wave ratio when properly matched to the coaxial line it is utilized with. Utilizing ceramic separators in thisfashion provides a connector which will function vat temperatures in excess of 600 F.

Although this invention has been described and illustrated in detail, it is to be clearly understood that the same is by way `of illustration and example only, and is not to be taken by way of limitation7 the spirit and scope dielectric coaxial lines, a center electrical conductor, an

electrically conductive shell concentric with and surrounding said center conductor, a gas dielectric interposed between said center conductor and said shell,`and a pair of hollow conical ceramic separator beads, said beads being identical as to dielectric constant, base angle, face angle a sleeve nut I12. To 'assure a good airtight connection,

formed with said center conductor, and face angle formed with said shell, `said separator beads being concentric lto said center conductor, the vertex ends of said beads facing each other and being bonded to adjacent sections of said center conductor, and the base ends -of said beads being bonded to the inner wall of said concentric shell.

2. In aV coaxial electrical connector for use with gas dielectric coaxial lines, a center electrical conductor, an electrically conductive shell concentric with and surrounding said center conductor, a gas dielectric interposed 1between said center yconductor and said shell, and a pair of Y hollow conical vceramic separator beads, said beads being identical las to dielectric constant, kbase angle, face angle formed with said center conductor, and .face angle formed with said shell, said .separator beads being Vconcentric to said center conductor, the vertex ends of said beadsfacing each other and being bonded to adjacent sect-ions `of said center conductor, the base ends of said beads `being bonded '-to lthe inner wall of said concentric shell, the base angles of ysaid conical beads'being equalV to each other and satisfying the relationship,

01=arc .tan 1' where 01 is equal to the base angles of said beads, K2 is the dielectric constantof the material of `said beads and K1 is the dielectric constant of 'said gasrdielectric. 3. YIn a coaxial electrical -connector for use'with `gas dielectric coaxial lines, a center electrical conductor, an electrically conductive shell concentric with `and surrounding said center conductor, a gas dielectric interposed hetween said center conductor vand said shell, a `pair of hollow conical ceramic separator beads, said beads being identical as to dielectric constant, base angle, face angle formed'with said center conductor and face angle formed with said shell, said separator beads being concentric to said center conductor, the vertex ends of said lbeads facing each other and being bonded -to 'adjacent sections ofsaid center conductor, the "base Iends of said 'beads being bonded to 4'the inner wall -o'f .said 'concentric shell, the

base angles of said conical beads being equal to each other and satisfying the relationship,

/K g 1; E 1 are an K1 where 01 is equal to the base angles of said beads, K2 is the dielectric constant of the material of said beads and K1 is the dielectric constant of said gas dielectric, a cylindrical electrically conductive ferrule adapted to be bonded to a tubular electrical conductor, and means for urging said ferrule against the end of said concentric shell in gas tight relationship thereto.

4. In a coaxial electrical connector for use with gas dielectric coaxial lines, a center electrical conductor, an electrically conductive shell concentric with and surrounding said center conductor, a gas dielectric interposed between said center conductor and said shell, anda pair of hollow conical ceramic separator beads, said beads being identical as to dielectric constant, base angle, face angle formed with said center conductor, and face angle iorm'ed with said shell, said separator beads being concentric to said center conductor, the vertex ends of said beads facing each other and being bonded to adjacent sections of said center conductor, the base ends of said beads being bonded to the inner wall of said concentric shell, the base angles of said conical beads being equal to each other and satisfying the relationship,

g Z: 6o mm2 u m tangal where Zc is any desired characteristic impedance, K2 is the dielectric constant of the material of said conical beads, qb, is the face angle formed between said conical beads and said center conductor and, pb is the face angle formed between said conical beads and said concentric shell.

5. In a coaxial electrical connector for use with gas dielectric coaxial lines, a center electrical conductor, an electrically conductive shell concentric with and surrounding said center conductor, said concentric shell having an undercut surface on its inner wall to provide an elective inductance, a gas dielectric interposed between said center conductor and said shell, a pair of hollow conical ceramic separator beads, said beads being identical as to dielectric constant, base angle, face angle formed with said center conductor and face angle formed with said shell, said separator beads being concentric to said center conductor, the vertex ends of said beads facing each other and being bonded to adjacent sections of said center conductor, the base ends of said beads being bonded to the inner wall of said concentric shell, the base angles of said conical beads being equal to each other and satisfying the relationship,

01=arc tan 6. In a coaxial electrical connector for use with gas dielectric coaxial lines, a center electrical conductor, an electrically conductive shell concentric with and surrounding said` center conductor, said concentric shell having an undercut surface in its inner wall to provide an effective inductance, a gas dielectric interposed between said center conductor and said shell, a pair of hollow conical ceramic separator beads, said beads being identical as to dielectric constant, base angle, face angle formed with said center conductor, and face angle formed with said shell, said separator beads being concentric to said center conductor, the vertex ends of said beads facing each other and being bonded to adjacent sections of said center conductor, the base ends of said beads being bonded to the inner wall of said concentric shell, the base angles of said conical beads being equal to each other and satisfying the relationship,

l: Kl 01 are tan 1 l K! where 6, is equal to the base angles of said beads, K2 is the dielectric constant of the material of said beads and K1 is the dielectric constant of said gas dielectric,

E Z= 6 0 1ntan2 VE tangE where Zo is any desired characteristic impedance, K2 is the dielectric constant of the material of said conical beads, e, is the face angle formed between said conical beads and said center conductor and, pb is the face angle formed between said conical beads and said concentric shell, a cylindrical electrically conductive ferrule adapted to be bonded to a tubular electrical conductor, and means for urging said ferrule against the end of said concentric shell in gas tight relationship thereto.

7. In a coaxial electrical connector for use with gas dielectric coaxial lines, a center electrical conductor, an electrically conductive shell concentric with and surrounding said center conductor, said concentric shell having an undercut surface in its inner wall to provide an effective inductance, air interposed as a dielectric between said center conductor, and said shell, and a pair of hollow conical separator beads fabricated of mica bonded glass having a dielectric constant of substantially 9.3, said beads being identical as to dielectric constant, base angle, face angle formed with said center conductor, and face angle formed with said shell, said separator beads being concentric to said center conductor, the vertex ends of said beads facing each other and being bonded to adjacent sections of said center conductor, the base ends of said beads being bonded to the inner wall of said concentric shell, the base angles of said beads being substantially equal to 72, the face angles of the junction of the vertex ends of said beads with said center conductor as measured from the longitudinal axis of said center conductor being substantially equal to 14, the face angles ot the junction of the base ends of said beads with said shell as measured from the longitudinal axis of said center conductor being substantially equal to 8. In a coaxial electrical connector, a center electrical conductor, an outer conductive shell concentric with said center conductor, a gas dielectric interposed between said inner and outer conductors, and a pair of hollow conical ceramic separator beads, said beads being identical as to dielectric constant, base angle, face angle formed with said center conductor, and face angle formed with said shell, said conical beads having base angles whose magnitude is a function of the dielectric constant of the bead ceramic material, said separator beads being concentric to said center conductor, the vertex ends of said beads facing each 'other and 4being bonded to adjacent sections of said center conductor, the base ends of said beads being bonded to the inner wall of said concentric shell.

9. The devicev as recited in claim 8 wherein the magnitudes of theface angles between said beads and said center conductor and `said beads and said outer conductor are a function of the dielectric constant of the ceramic material of saidrbeads.

References Cited inthe file of this patent 'UNITEDSTATES PATENTS 2,406,945 F611 sept. 3, 1946 Appiication OTHER REFERENCES Y of Brewsters Angle to the Design of Coaxialline Components for Microwaves, RCA Review, 10 vol. 15V, pages 23S-251. 

